What's SpongeBob SquarePants without Squidward? Jimmy Neutron without Carl? Dare I say, Rugrats without Cynthia, the inanimate, screwed-up doll of Angelica's?
Most of the time, the greatest characters in a series are the ones who the show isn't even about. Sure, some of the following are main characters, but the bulk are side characters—the ones who didn't get enough screen time but should've. In no specific order, these are 23 of the best Nickelodeon characters to ever wander past our screens.